Conventionally, there have been used Ni—Fe alloys, typified by JIS PC permalloy, having a high magnetic permeability, and soft magnetic materials which are of modifications of the Ni—Fe alloys further containing additive Mo or Cu, and having further improved magnetic permeability.
Also, with a view to materializing a further high magnetic permeability, there has been proposed a soft magnetic material, which has a high magnetic permeability being of a relative magnetic permeability exceeding 250,000 under a magnetic field of 0.4 A/m being defined as an initial, relative magnetic permeability in JIS C2531, and which can be obtained by adjusting quantities of not only main components of the material but also impurities such as B, N, etc. in appropriate ranges and further controlling an atmosphere and a cooling rate in appropriate ranges when conducting final heat treatment (see, for example, JP-A-3-75327).
This proposal is of an excellent technology in the point that the magnetic permeability of a soft magnetic material, which has a great influence on a magnetic shielding property, is improved.